1. Field of the Invention
This invention relates to a capacitor-type power supply unit, and more particularly to a capacitor-type power supply unit for electric vehicles.
2. Prior Art
Conventionally, a capacitor-type power supply unit of this kind includes at least two capacitor blocks each having a plurality of capacitor cells connected in series via a bus bar, and a plurality of electronic circuits connected to the capacitor cells, for controlling the operation of each capacitor cell.
Further, the capacitor cells of the capacitor blocks, which are connected in series, may employ approximately one hundred of electric double-layer capacitors, each of which has an output voltage of 3.5 volts. Therefore, one capacitor block provides an output voltage of approximately 350 volts when it is fully charged. This kind of capacitor-type power supply unit is used in such a manner that the connection of the two capacitor blocks is changed over between parallel connection and series connection depending on the amount of a remaining electric charge stored therein, operating conditions of an engine installed on the automotive vehicle, and traveling conditions of the vehicle.
In the conventional capacitor-type power supply unit, the electric circuits are not provided integrally with the capacitor cells, but are mounted at a location remote therefrom, e.g. at a part of a pulse width modulation (PWM) driver as a motor driver (PDU) or in the vicinity of a motor.
Since in the conventional capacitor-type power supply unit for electric vehicles, the electronic circuits are not provided integrally with the capacitor cells, but are mounted at a location remote therefrom, the wiring between the terminals of the capacitor cells and the electronic circuits tends to become long with large impedance, which causes a large voltage drop in the capacitor cells of the capacitor-type power supply unit.